Selection of evaluation criteria for oil-free air compressors

If you determine the size and type of compressor, but there is a problem is the choice of oil lubrication or oil-free air compressor. In order not to make the answer too complicated, your choice should be based on the application of compressed air.

Do I need an oil-free compressor?

The first step in selecting a compressor is to evaluate the needs of the equipment. In some cases, the consequences of oil pollution is too high, in this case the use of oil-free air compressor is necessary. However, most manufacturing industries, industrial plants and small workshops are suitable for the use of oil-lubricated compressors, because the consequences of oil contamination in these applications will not be as serious as the consequences of contaminated food production facilities. The role of the oil in the air compressor is to lubricate, seal and cool the compressed air.

If there is no exact need to use oil-free compressed air, a more economical method is to use oil-lubricated compressors such as oil-injected screw compressors. Oil-free compressors are much more expensive than oil-lubricated compressors. Although there are traces of oil in compressed air, these oils can be filtered through the use of appropriate air filtration products. The use of coalescing filter can purify the dust contained in the compressed air to 0.01 microns. If the activated carbon filter is further purified, the air cleanliness level 1 can be achieved.

How to judge the air cleanliness level?

Oil-free air compressors are used to produce a variety of oil-sensitive products, such as semiconductors, pharmaceuticals and paper. In the production process of these products, even a small amount of oil may have an adverse effect on the product and even people. Class 0 oil-free (Class 0) and "technical oil-free" are usually used to indicate that the compressor meets the oil-free requirements of certain standards. Although these terms are similar, if their key differences are not considered, they may lead to unintended consequences.

To better understand all this, let's take a deeper look at what "oil-free" means. Oil-free is used to describe a compressor in which the compression chamber of the compressor does not use any lubrication. This term describes a type of compressor. Class 0 and "technical oil-free" indicate the cleanliness of the air after being filtered. There are some important differences between the two, which we will explain later in this article.

The International Organization for Standardization (ISO) sets global standards for civil, industrial and commercial products. The compressed air industry also has its own set of ISO standards. According to the final air cleanliness (determined by the number of particles per cubic meter and considering the particle size), the compressed air cleanliness level ISO is divided into six levels: 0-5. The original 1991 version of the ISO compressed air purity standard was developed by filter manufacturers and tailored for their filter products, with only five grades of cleanliness based on oil content, the best of which is Grade 1.

ISO Cleanliness Level 1: Technical oil-free

compressed air with cleanliness level 1 stipulates that the oil content is 0.01 mg/m3 at 1bar (a) and 20 ℃. When compressed air meets this standard through filtration, it is called "technically oil-free". The standard was revised in 2001 and updated in 2010. Current standards set limits for oil content (aerosols, liquid oils and oil vapors) and specify specific measurement criteria for oil vapors.

ISO cleanliness level 0: really no oil

the new ISO standard adds a new level of cleanliness (class 0) to meet more stringent quality requirements. Level 0 is the cleanest level. They can guarantee 100 percent oil-free air. There are some misconceptions in the industry that promote oil-lubricated compressors with filters, calling them "technically oil-free" and claiming that air quality is often better than oil-free compressors. These claims are untrue, and accidental damage to sensitive products and equipment can occur when Class 0 clean air is required but only Class 1 air is used.

When choosing an oil-free compressor, make sure to choose a 0-stage oil-free compressor instead of a "technical oil-free" product. Although the initial price of a 0-stage oil-free compressor is usually higher, this option is much safer in sensitive applications. If it is level 0 compressed air, you can ensure that your terminal equipment will never be contaminated and that your equipment assets are protected. When choosing an oil-free or oil-lubricated air compressor, the best practice is always to seek the advice of a compressed air professional.